Method for producing light-sensitive coatings on metal webs



MEARS METHOD FOR PRODUCING LIGHTr-SENSITIVE June 14, 1955 N. B.

COATING 0N METAL WEBS Original Filed April 19, 1951 5 She ets-Sheet 1INVE NTOR NORMAN B. MEARS- ATTORNEY June 14, 1955 N. B. MEARS 2,710,314

METHOD FOR PRODUCING LIGHT-SENSITIVE COATING 0N METAL WEBS OriginalFiled April 19, 1951 5 Sheets-Sheet 2 FIG. 4

43 44 FIG. 5

INVENTOR NORMAN B. MEARS ATTORNEY June 14, 1955 N. B. MEARS 2,710,314

METHOD FOR PRODUCING LIGHT-SENSITIVE comma on METAL WEBS Original FiledApril 19, 1951 5 Sheets-Sheet 3 NVENTO NORMAN 5 MEARS ATTORNEY June 14,1955 Original Filed April 19, 1951 N. B. MEARS METHOD FOR PRODUCINGLIGHT-SENSITIVE COATING ON METAL WEBS 5 Sheets-Sheet 4 FIG. I?

FIG. l4

FIG. l5

INVENTOR NORMAN B. MEARS ATTORNEY June 14, 1955 N. B. MEARS 2,710,814METHOD FOR PRODUCING LIGHT-SENSITIVE COATING ON METAL WEBS OriginalFiled April 19, 1951 5 Sheets-Sheet 5 2 FlG.l9 RG20 I111 I 32v--\ 32,/23 1 II 4' II M E -J a l I iNVENTOR NORMAN B. MEARS AT TORN S fineMETHDD FUR PRGDUCKNG LKGHT-SENSETWE COATINGS N METAL WEBS Norman E.Mears, West St. Paul, Minn assignor to Enclrbee-Mears Ccmpany, St. Paul,Minn, a corporation of Minnesota Original applicatien April 19, 1951,Serial No. 221,904. Divided and this application May 24, 1952, SerialNo. 290,511

Claims. (Cl. 117-34) In the manufacture of various articles of precisionfrom thin metal blanks, sheets or webs requiring photographicreproduction of a pattern or design on the work, a large amount of handwork and time has heretofore been required in the preparation, coatingand drying of the work preparatory to the photo-printing of the requireddesign on the sensitized surface or surfaces. The present inventionrelates to an improved machine and method for performing suchpreliminary operations, including the coating and drying of the work.

It is an object of my invention to provide a machine which operatesautomatically to prepare the surfaces of thin metal webs and apply auniform light-sensitive coating thereto whereby the cost of the coatedproduct is reduced and a uniform, continuous coating of high quality isobtained.

A particular object is to provide a machine of the class described whichis adapted to receive the web to be coated from a spool or reel and tomove the web continuously along a determined path in such position as toexpose one or both faces of the web for treatment in combination withdevices positioned along the path of travel of the web for cleaning andscrubbing both faces or a selected face thereof and to form fine toothedsurfaces thereon, then coating such surface or surfaces with a liquidlight-sensitive material, then drying the coating material and finallywinding the coated, dry web on a spool or reel from which it may bereadily withdrawn for further treatment.

A further object is to provide an improved method for uniformly coatinga thin, flexible metal web with a light sensitive material while movingthe web continuously along a determined path and in a vertical plane,the method including the steps of delivering the coating in a liquidstate to the upper edge of the web so that the liquid is caused to flowover both faces or a selected surface of the web, allowing the excesscoating material to drain from the lower edge while removingaccumulations of the coating from the lower longitudinal margin andthereafter drying the coating.

Among the articles of manufacture which may be improved and reduced incost by the use of the present invention are apertured masks fortelevision tubes, fine screens for mechanical separation of solidparticles, reticles for fire control and sighting instruments and otherarticles requiring precise location of minute perforations in thin metalblanks. For such articles the metal web or sheet is less than .02 inchthick and is usually within the range .001 to .006 inch thick. Puremetals, e. g., copper, silver, nickel or tin are best suited foraccurately controlled etching treatment and the web should be of uniformthickness. Thin webs of this character are difiicult to handle becauseof their malleability, flexibility and general tendency to becomelocally deformed as by wrinkles, creases and other indentations whichdestroy the accuracy and utility of the product. By the presentinvention such detrimental deformations are eliminated and importanteconomies in the quantity production of coated webs of any requiredwidth are obtained.

Referring to the accompanying drawings which illustrate my improvedmachine and method by way of example and not for the purpose oflimitation:

Figure 1 is a diagrammatic plan view of the machine;

Fig. 2 is a side elevational view showing the portions of the machineextending from the feed roll to the coating mechanism and including thecleansing and scouring mechanism;

Fig. 3 is a fragmentary cross sectional View taken on the line 3-3 ofFig. 2;

Fig. 4 is a fragmentary cross sectional view taken on the line 4-4 ofFig. 2;

Fig. 5 is a fragmentary section taken on the line 5-5 of Fig. 5;

Fig. 6 is a fragmentary section taken on the line 6-6 of Fig. 2;

Fig. 7 is a side elevational view showing the coating mechanism;

Fig. 8 is a fragmentary cross sectional view taken approximately on theline 8-8 of Fig. 7;

Figs. 9 and 10 are side elevational and plan views respectively of thedrain trough and associated devices for removing the excess coating;

Fig. 11 is a cross section taken on the line 11-11 of Fig. 9;

Fig. 12 is a fragmentary section taken on the line 12-12 of Fig. 11;

Fig. 13 is a section taken approximately on the line 13-13 of Fig. 7;

Fig. 14 is a detail side elevational view showing the nozzle fordelivering the coating liquid to the web and the support therefor;

Fig. 15 is a section taken on the line 15-15 of Fig. 14;

Fig. 16 is a cross section taken through the degreasing chamberapproximately on the line 16-16 of Fig. 2;

Fig. 17 is a diagrammatic horizontal sectional view through the driertaken on the line 17-17 of Fig. 18;

Fig. 18 is a side elevational view of the drier;

Fig. 19 is a side elevational view showing the powerdriven reel at thedelivery end of the machine and associated mechanism, and

Fig. 20 is a cross sectional view taken approximately on the line 20-20of Fig. 19.

Referring to the diagrammatic illustration of the machine and methodshown in Fig. 1, the numeral 21 indicates a reel or spool from which ametal web 22 to be coated is continuously drawn. This web preferablyextends in a vertical plane from the reel 21 to a powerdriven reel 23 atthe opposite end of the machine so that the longitudinal edges of theweb extend horizontally, one above the other. Between the reels 21 and23 the web 22 is supported in its upright position between pairs ofrollers 24 and 25 which grip and confine the upper and lower margins ofthe web, leaving both faces thereof exposed for treatment. As it iswithdrawn from the reel 21, the web 22 is first given a degreasingtreatment in a chamber 26. This chamber may contain a gas such astrichlorethylene which reacts with any grease or oil that may be carriedby the surface of the web to facilitate the subsequent thoroughcleansing of the surfaces or the degreasing agent may be applied in theform of a spray or by brushing it on the surfaces to be cleansed.

After passing out of the degreasing chamber 26, the web 22 is supportedby pairs of the rollers 24 and then passes through a cleansing sectionof the machine wherein pairs of brushes 27 are operated in engagementwith opposite faces of the web while water and a suitable detergent anda fine abrasive material are applied to the web. After thorough scouringand rinsing in the cleans- It ing section of the machine the web passesto and through a coating and drainage section wherein a suitable lightsensitive coating material is caused to flow over the faces of the webfrom a reservoir 28 and the excess liquid is recovered in a trough 29extending along the lower edge of the web. From the coating section theweb passes through a drier 30 in which filtered and heated air isdirected over the coated surfaces to be dried. Finally the coated anddried web 22:: passes to a reel 23 upon which it is wound, together witha protective web of paper 31 which is drawn from a roll 32 so that acontinuous web of paper is interposed between successive convolutions ofthe web 22:: on the reel 23.

Degreasing As shown in Fig. 2, the reel 21 is mounted on a verticalspindle 33 having suitable bearings in the frame of the machine. Thedegreasing chamber 26 (Figs. 2 and 1.6) may comprise a tank containing aliquid 34 such as trichlorethylene which may be applied in any suitablemanner to the surfaces of the metal, e. g., by brushing, spraying, or asa gas. Since the degreasing agent boils at 180 F. to form a heavy gas itmay be heated by a heating coil 35 in the bottom of the tank. The web 22to be coated enters and leaves the chamber 26 through suitablevertically elongated slots therein and the slots are sealed by flexiblemembers 36 engaging opposite faces of the web 22 in order to prevent theescape of the toxic gas.

Cleansing From the degreaser the web 22 passes between pairs of thebrushes 27 which are supported on pairs of horizontally extending bars38, as best shown in Figs. 2, 4, 5 and 6. The bars 38 are supported forvertical reciprocating movement, being connected at each end tovertically elongated slide members 39, each slidable along a verticalguide rod 48. Each of the members 39 is operatively connected to an arm41 having an eccentric connection with a horizontal drive shaft 42. Apair of the shafts 42 extend along the top of the supporting frame andare operatively connected through suitable speed reducing mechanism in ahousing 43 to an electric motor 44. Thus when the machine is inoperation the motor 44 through its connections with the brushes 27,causes these brushes to be given reciprocating movement with thebristles of the brushes at opposite faces of the Web 22 in contacttherewith.

Water is supplied and caused to flow downward between each pair ofbrushes and over the surfaces of the web 22 from a series of pipes 45. Adetergent, preferably including a fine abrasive material, is alsosupplied to the web between certain of the brushes 27 toward thereceiving end of the cleansing section and clear wash water is thensupplied as a spray to the web and brushes near the delivery end of thissection. As a result of the treatment in the cleansing section of themachine, the web 22 is thoroughly cleaned and given a fine grained burrsurface best suited to the adherence of the light sensitive coatingsubsequently applied in the machine. The used washing fluid, detergentand abrasive material flows from the lower edge of the web 22 and lowerends of the brushes 27 into a pan 46 and thence to waste. Soft rubberWipers or squeegees 27a (Figs. 7 and 13) are arranged to remove excesswash water from the web 22 as it passes to the coating section.

Coating Referring particularly to Figs. 7-15 inclusive, a suitable coldtop or hot top enamel, e. g., a glue top enamel, in liquid state is fedfrom the overhead tank 23 through a tube 47 to a nozzle 48 disposed todischarge a stream of the liquid upon the upper edge of the web 22 asthe latter is advanced at a predetermined rate of speed. As best shownin Figs. 14 and 15, the nozzle 48 is formed with an aperture 49 at itslower end adapted to receive the upper margin of the web 22 and todirect the coating liquid over both faces of the web. The coating fluidis thus caused to cover both faces of the web and the excess drains fromthe lower edge into the elongated trough 29. Accumulations of the liquidin this trough are withdrawn through a tube 50 and are returned by amotor'driven pump 51 (Figs. 7 and 8) and tube 52 to the tank 28.

Spaced along the trough 29 are a plurality of wiping devices 53 in thenature of Squeegees which engage both faces of the lower margin of theweb 22 to positively remove the excess of the liquid which tends toadhere and accumulate along the lower margin. As shown in detail inFigs. 11 and 12, each of the wiping devices 53 is provided with aflexible elastic blade 54, preferably constructed from rubber orrubber-like material, and formed with a vertical slot 55 extending tothe upper edge of the blade to receive the lower margin of the web 22.As the lower margin of the web moves along in the slots 55,accumulations of the coating material are positively removed by theseveral blades 54 from which the excess liquid passes by gravity intothe trough 29. The blocks supporting the blades 54 are readily removablefrom U-shaped holders 53a fixed on the side walls of the trough 29.

Any of a number of commercially available or suitable light sensitiveenamels may be employed as the coating material. For example, a hot topsolution of glue and ammonium bichromate has been used with excellentresults. When dry it forms a sufficiently durable coating and issufficiently stable to permit storage of the rolls of coated metal forperiods of a number of weeks when it is convenient or desirable to deferthe photo-printing for such periods.

Drying When the web 22 reaches the delivery end of the coating section,the light sensitive coatin is in a tacky, nonfluid condition ready fordrying and the web passes into the drying chamber indicated generally bythe numeral 30. Since details of the dryer are not'claimed herein, theyare merely illustrated diagrammatically. As best shown in Figs. 17 and18, the dryer has a generally rectangular casing 3911 which is formedwith an inlet opening for air covered by a suitable filter 56 throughwhich the air is drawn into a conduit 57 within the casing. This conduitextends to the intake of a power-driven centrifugal fan 58 and the airis heated by a multiplicity of electrical heating elements 59 located inthe conduit 57. The heated air is blown from outlets 60 and 6t locatedat one end of the heating chamber so that the air is caused to passalong opposite surfaces of the web 22 during its passage through thechamber. From the opposite end of the drying chamber the air may bedischarged through a conduit 62 to atmosphere under control of a damper63 and a portion of the air may be returned to the conduit 57 through abranch conduit 54 under control of a damper 65. Suitable controls forthe fan motor and heating elements are indicated at 66, on the exteriorof the dryer, which is also provided with an instrument indicating thetemperature within the heating chamber and an access door 67. Uponemerging from the drying chamber the light-sensitive coating on the web2211 is sufiiciently hard and dry to permit the winding of the web onthe reel 23.

Winding mechanism As shown in Figs. 19 and 20, the web 2211, as itemerges from the dryer 30, passes partly around a guide roller 68 andthence to the periphery of the reel 23. This reel is continuouslyrotated at a predetermined controlled speed through suitable connectionswith an electric motor 69, including speed reducing mechanism 79 and afriction drive connection with a vertical shaft 71 on which the reel 23is fixed. In order to protect the sensitized surfaces of the coated web,the web 31 of paper or other suitable material is continuously drawnfrom a roll 32 and is wound between convolutions of the web 22a on thereel 23.

In order to obtain the desired smooth uniform coating on the web it isimportant to allow time for the excess liquid coating to drain from theweb surfaces, with the aid of the wiper devices 53, and also time forthe lightsensitive material remaining on the web to become tacky andnon-fluid before the web passes into the dryer 30 Where the accelerated,final stage of drying takes place. The time required for the preliminarydrying at room temperature is, of course, dependent upon the liquidsolvent content of the coating material and the room temperature andhumidity. The rate of travel of the web is adjusted to compensate forthe atmospheric conditions and liquid content of the coating materialand so that the required preliminary drying will take place during thetravel of any given point on the web from the coating nozzle 48 to thedrying chamber 30. It has been found that in the production oftelevision masks for which webs of Widths within the range 6 inches to30 inches and where a hot top enamel such as that hereinbefore describedis employed, a suitable rate of travel of the web is between one and twofeet per minute and that the drainage and preliminary drying at roomtemperature should be continued for a period of from 3 to 6 minutes,depending on atmospheric conditions.

Sufiicient tension to retain the web in its vertical position and out ofcontact with the adjacent machine parts as it passes along the coatingand drying sections of the machine is created by the friction or drag ofthe scrubbing and cleaning devices and by the turning of the feed reel21 on its support. Care is thus taken to avoid contact with the coatedsurfaces of the web until after they have been thoroughly dried.

The present application is a division of my application Serial No.221,904, filed April 19, 1951, for Machine and Method for ProducingLight-Sensitive Coatings on Metal Webs.

Having described my invention, what I claim as new and desire to protectby Letters Patent is:

1. The method of coating a thin metal web which comprises, continuouslymoving said web along a determined path in a substantially verticalplane with one longitudinal edge above the other longitudinal edge whilesuecessively cleansing a surface thereof, then delivering a stream ofliquid light-sensitive enamel to said surface solely along the uppermargin thereof whereby said surface is coated by flow of the liquidenamel crosswise of the direction of movement of the web along said pathand then drying the coating.

2. The method of coating a thin metal web which comprises, continuouslymoving said web along a determined path and in a substantially verticalplane with one longitudinal edge above the other longitudinal edge whilesuccessively cleansing the surfaces thereof, removing the excesscleaning material from the web, then delivering a liquid light-sensitivematerial as a stream solely upon and along the upper margins of thecleansed surfaces while draining the excess liquid from the lowermargins thereof, drying the resulting coated surfaces and winding thecoated and dried web in the form of a roll.

3. The method of coating a thin metal web which comprises, continuouslymoving said web along a determined path in a substantially verticalplane with one longitudinal edge above the other longitudinal edge,delivering a stream of liquid light-sensitive material solely upon zonesextending along the upper edge of said web to thereby coat the surfacesof the web while draining and removing the excess coating liquid fromthe lower 'edge of the web for a period of time sufiicient to allow thecoating to become tacky and non-fluid and then drying the coating.

4. The method in accordance with claim 3 wherein the removal of theexcess coating liquid from the lower edge of the web is effected bypositive wiping of a relatively narrow marginal area of the web adjacentto the lower edge thereof.

5. The method in accordance with claim 3 wherein the web is maintainedunder longitudinal tension sufficient to retain a major portion of thecoated web in self-supporting spaced relation to all elements of thecoating and drying apparatus.

References Cited in the file of this patent UNITED STATES PATENTS415,566 Rowell Nov. 19, 1889 2,021,485 Huebner Nov. 19, 1935 2,235,978Braucher Mar. 25, 1941 2,279,686 Kerlin Apr. 14, 1942 2,469,123 MartinMay 3, 1949

1. THE METHOD OF COATING A THIN MATAL WEB WHICH COMPRISES, CONTINUOUSLYMOVING SAID WEB ALONG A DETERMINED PATH IN A SUBSTANTIALLY VERTICALPLANE WITH ONE LONGITUDINAL EDGE ABOVE THE OTHER LONGITUDINAL EDGE WHILESUCCESSIVELY CLEANSING A SURFACE THEREOF, THEN DELIVERING A STREAM OFLIQUID LIGHT-SENSITIVE ENAMEL TO SAID SURFACE SOLELY ALONG THE UPPERMARGIN THEREOF WHEREBY SAID SURFACE IS COATED BY FLOW OF THE LIQUIDENAMEL CROSSWISE OF THE DIRECTION OF MOVEMENT OF THE WEB ALONG SAID PATHAND THEN DRYING THE COATING.